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9

Narrow Channels

Left: vessels under 20 m and sailing vessels shall not impede a vessel that can safely navigate only within the channel. Right: fishing shall not impede any other vessel navigating there. Schematic depths are not navigation data.

1The rule in plain words

In one sentence…

In a narrow channel, keep as near as safe and practicable to the outer limit on your starboard side.

Where do you navigate?

When proceeding along a narrow channel or fairway, keep near the outer limit on your starboard side, when it is safe to do so.

Who must not impede?

Vessels under 20 metres and sailing vessels must not impede vessels able to navigate safely only within the channel; fishing vessels must not impede any vessel navigating within it. Do not cross if you impede that passage.

How do you overtake in a channel?

If the overtaken vessel must manoeuvre, indicate intention with Rule 34(c)(i). If agreeing, the overtaken vessel sounds 34(c)(ii) and enables safe passing. At an obscured bend, be alert and cautious; sound the appropriate Rule 34(e) signal.

What about anchoring?

In a narrow channel, avoid anchoring if the circumstances of the case admit.

2Key points

  1. 1.

    Narrow channel → outer starboard limit · no danger.

  2. 2.

    Less than 20 metres or sailing → do not impede the channel-restricted vessel.

  3. 3.

    Conditional overtaking → intention · agreement · action.

  4. 4.

    Obscured bend → alertness, caution and Rule 34(e) · avoid anchoring.

3Frequent mistakes

  • Wrong: "At 20 metres I am still below 20 metres."

    Right: "Less than 20 metres": a vessel exactly 20 metres is outside that threshold.

  • Wrong: "I may cross even if I block the channel vessel."

    Right: Do not cross if you impede the vessel that can safely navigate only within the channel.

  • Wrong: "One whistle is enough to overtake."

    Right: Indicate intention, get agreement, permit safe passing, and keep the Rule 13 obligation.

4Exam keys & interpretation

Exam keys

  • "Less than 20 metres": a vessel exactly 20 metres is outside that threshold.

  • For a crossing, look for "if it impedes" and the vessel that can navigate only within.

  • For conditional overtaking, separate intention, agreement and action; Rule 13 still applies.

How to read it

  • The no-impeding duty depends on the vessel type and on whether the other vessel can navigate only within the channel.

  • Conditional overtaking needs the overtaking vessel's intention, the other vessel's agreement and her action; Rule 13 remains.

5Official text

IMO COLREG 1972U.S. Coast Guard — International Navigation Rules (2024)

Full wording of the rule, reproduced from the official source below.

(a) A vessel proceeding along the course of a narrow channel or fairway shall keep as near to the outer limit of the channel or fairway which lies on her starboard side as is safe and practicable. (b) A vessel of less than 20 meters in length or a sailing vessel shall not impede the passage of a vessel which can safely navigate only within a narrow channel or fairway. (c) A vessel engaged in fishing shall not impede the passage of any other vessel navigating within a narrow channel or fairway. (d) A vessel shall not cross a narrow channel or fairway if such crossing impedes the passage of a vessel which can safely navigate only within such channel or fairway. The latter vessel may use the sound signal prescribed in Rule 34(d) if in doubt as to the intention of the crossing vessel. (e) (i) In a narrow channel or fairway when overtaking can take place only if the vessel to be overtaken has to take action to permit safe passing, the vessel intending to overtake shall indicate her intention by sounding the appropriate signal prescribed in Rule 34(c)(i). The vessel to be overtaken shall, if in agreement, sound the appropriate signal prescribed in Rule 34(c)(ii) and take steps to permit safe passing. If in doubt she may sound the signals prescribed in Rule 34(d). (ii) This Rule does not relieve the overtaking vessel of her obligation under Rule 13. (f) A vessel nearing a bend or an area of a narrow channel or fairway where other vessels may be obscured by an intervening obstruction shall navigate with particular alertness and caution and shall sound the appropriate signal prescribed in Rule 34(e). (g) Any vessel shall, if the circumstances of the case admit, avoid anchoring in a narrow channel.
Source:

6Test your knowledge

Question 1/4

When proceeding along a narrow channel or fairway, what should you do?

More questions on this rule →

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Frequently asked questions about COLREG Rule 9

Which side of a narrow channel must a vessel keep to?

A vessel proceeding along the course of a narrow channel or fairway shall keep as near to the outer limit of the channel which lies on her starboard side as is safe and practicable (Rule 9(a)).

Under which circumstances may a vessel anchor in a narrow channel?

Rule 9(g) requires any vessel to avoid anchoring in a narrow channel if the circumstances of the case admit. The rule does not define an emergency-only exception; assess whether avoiding anchoring is possible in the actual circumstances.

Which vessels must not impede a vessel navigating in a narrow channel?

A vessel of less than 20 metres in length or a sailing vessel shall not impede a vessel that can safely navigate only within a narrow channel or fairway (Rule 9(b)), and a vessel engaged in fishing shall not impede any other vessel navigating within the channel or fairway (Rule 9(c)).

How do overtaking and crossing work in a narrow channel?

If safe overtaking requires the vessel ahead to take action, the overtaker signals her intention and the vessel ahead, if agreeing, signals agreement and takes steps to permit safe passing (Rule 9(e)); the overtaker remains bound by Rule 13. A vessel shall not cross the channel if crossing would impede a vessel that can safely navigate only within it (Rule 9(d)).